Further to Marshall's post:   ... and if you want to use  tr/// to reduce multiple occurrences of a character to a single translated character, there's the  /s (squash) modifier (see  tr/// in Quote-Like Operators in perlop):

c:\@Work\Perl\monks>perl -wMstrict -le
"my $str = 'a+ +test+lotsapluses+++++++test';
 print qq{'$str'};
 ;;
 $str =~ tr{+}{ }s;
 print qq{'$str'};
"
'a+ +test+lotsapluses+++++++test'
'a   test lotsapluses test'
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